Conventionally, in order to control the transmittance of light generated from a welding or cutting torch, a dazzle prevention device, which is worn on the head of an operator and equipped with an optical detection means, has been used.
FIG. 1 is a perspective view showing a protective mask 1 equipped with a conventional dazzle prevention device 2.
As shown in FIG. 1, the protective mask 1 provided with the dazzle prevention device on the front of the protective mask 1 reduces the illuminance of light, which is applied to the eyes of an operator, through a dazzle prevention plate 5, that is, a Liquid Crystal Display (LCD) included in the dazzle prevention device 2.
In more detail, an optical detection means 4, such as a photodiode provided on the front of the dazzle prevention means 2 detects light generated from a welding or cutting torch, and a control circuit contained in the dazzle prevention device 2 performs control so that the dazzle prevention plate 5 is darkened to reduce the illuminance of light passing through the dazzle prevention plate, thus protecting the eyes of an operator.
FIG. 2 is a view showing a user interface for allowing a user to adjust the shading, light detection sensitivity and delay of the conventional dazzle prevention device 2.
Referring to FIG. 2, the user interface of the conventional dazzle prevention device 2 includes a shade adjusting means 6, a light detection sensitivity adjusting means 7, and a delay adjusting means 8.
The shade adjusting means 6 functions to adjust the shade number of the dazzle prevention plate 5. The shade number indicates the degree of darkness of the dazzle prevention plate 5. When the shade number is adjusted using the shade adjusting means 6, the transmissivity of the dazzle prevention plate 5 is adjusted.
The light detection sensitivity adjusting means 7 functions to adjust the light detection sensitivity of the dazzle prevention device 2. The light detection sensitivity is a numerical value that indicates the degree to which the control circuit responds to the output signal of the light sensor means 4. As the light detection sensitivity increases, the control circuit can respond better to the signal under low luminance.
The delay adjusting means 8 functions to adjust the delay of the dazzle prevention device 2. In the case where a delay number is low, the control circuit of the dazzle prevention device 2 switches the dazzle prevention plate 5 from a dark state to a light state when the light sensor means 4 detects the completion of welding work. In contrast, in the case where the delay number is high, a longer time is required for switching from a dark state to a light state.
Generally, in the dazzle prevention device-related field, 5˜13 is used as the range of shade numbers, 0˜10 is used as the range of light detection sensitivity numbers, and 0˜10 is used as the range of delay numbers.
The user interface of the conventional dazzle prevention device 2 further includes a power switch 9 for selectively turning on and off power, a battery 10 for supplying power, and a low voltage indicator 11 for indicating the low voltage state of the device.
However, in the case where only the optical detection means is used erroneous operation has occurred frequently due to the difference between detected signals, which may occur according to the type of welding or welding machine, and coherent light.
That is, in the case where only the optical detection means is used the light detection sensitivity increases at the time of low current welding, outdoor welding and thin plate welding, in which case there occurs erroneous operation in that the dazzle prevention plate 5 does not lighten or lightens excessively slowly notwithstanding that the dazzle prevention plate 5 mist lighten in response to surrounding coherent light.
In order to prevent the above-described erroneous operation, a dazzle prevention device additionally equipped with an electromagnetic wave detection means is disclosed.
The conventional dazzle prevention device equipped with the electromagnetic wave detection means can effectively control the light transmittance of the dazzle prevention plate using an electromagnetic wave detection method during outdoor work exposed to sunbeams, during low current welding in which the illuminance of welding light is not significantly higher than illuminance of an environment, or in an environment in which it is difficult to identify welding light because the illuminance of the environment is high due to the use of a light having high directionality and high illuminance and thus, light other than the welding light is detected at the time of detecting light.
However, the conventional dazzle prevention device equipped with the electromagnetic wave detection means is disadvantageous in that it is set to use the electromagnetic wave detection method regardless of environmental conditions, so that in an environment where plenty of electromagnetic waves are generated the light transmittance of the dazzle prevention plate is unnecessarily lowered during work based on electromagnetic waves generated in the environment other than the welding or cutting torch of the operator, thus disturbing the precise operation of the operator.
Furthermore, in the conventional dazzle prevention device equipped with the electromagnetic wave detection means, electromagnetic wave detection sensitivity is fixed so that electromagnetic waves, which are generated by sources other than the machine of the operator, such as an electromagnetic wave generated by the machine of some other operator, can be detected thus resulting in erroneous operation.
Furthermore, the conventional dazzle prevention device equipped with the electromagnetic wave detection means is disadvantageous in that although the operator must precisely identify a welding or cutting area before starting work, an electromagnetic wave is generated prior to light at the time of applying power to a welding or cutting machine or turning on a welding or cutting start switch because the optical detection means and the electromagnetic wave detection means are constructed to independently operate, so that light transmittance is lowered based on a detected electromagnetic wave even though light is not generated thus hindering the operator from performing work after identifying a precise welding or cutting area.